Apparatus for electrolytic analysis



June 23, 1953 R. w. NOTVEST APPARATUS FOR ELECTROLYTIC ANALYSIS OriginalFiled Feb. 10, 1948 Patented June 23, 9

UNITED STATES APPARATUS FOR ELECTROLYTIC ANALYSIS Robert W. N otvest,Affton, Mo., assig-nor to Amere ican Brake Shoe Company, New York, N.Y,, a corporation of Delaware V Original application February 10, 1948,Serial No.

PATENT OFFICE 7,366. Divided and this application February 7, 1951,Serial No. 209,841

adhere firmly to the anode whereas, on the other hand, reducing gasessuch as H2 and NH3 tend, of course, to migrate to but do not tend to adhere firmly to the cathode. However, the adher- This invention relatesto an apparatus for the 5 ence of such oxidizing gases as N02 and 02upon electrolytic quantitative analysis or determ-inathe anode tends tobuild up the internal resistance tion of copper and lead incopper-bearing and of the electrolyte, thereby causing excessiveoverlead-bearing metals or alloys. voltage with resulting formation ofspongy and In the quantitative analytical determination irregula andloosely adhering deposits of metalor analysis of copper and lead incopper-bearing he copper and F002 upon the cathode and anode, andlead-bearing metals or alloys, or other specirespectively. mens, in acidsolutions, these metals are electro- The foregoing and other problemswhich are lytically deposited as metallic copper and as lead involved inthe quantitative electrolytic determioxide (P1002) upon a platinum wiregauze cathnation of copper and lead have been recognized ode and anode,respectively, of known weight. In heretofore in the art and attemptshave been the case of copper, the copper content of the made in variousways to overcome these difficulmetal or other specimen under analysis isthen ties. Thus, for example, mechanical electrolyte determined bycalculating the difference in the stirring devices, rotating electrodes,and other weight of the platinum cathode before and after mechanicaldevices have been employed and air the copper is deposited thereon.Similarly, in the stirring of the anode by the introduction of air caseof lead, the lead content of a metal or other into the electrolyte haveall been employed. l-Iowspecimen under analysis is calculated bydeterever, none of these prior mechanical devices or mining the weightof the lead oxide deposited methods has, insofarasI-am aware, beenentirely upon the platinum anode and then calculating successful, for anumber of reasons. Thus one the weight of the lead in the deposited leadoxof the serious difficulties involved in the use of ide in accordancewith the percentage composimechanical electrolyte stirring devices isthe fact tion of the lead oxide. that such mechanical electrolytestirring devices However, a number of problems have been ex..- tend todislodge the deposits of pp d 0? perienced heretofore in theelectroanalysis of from the cathode and anodaresp iv ly,Wh copper andlead in acid solutions and these probas agitation or scouring 0f heanode with air. lems have not heretofore, insofar .as I am aware, Whiletending o dislodge the firmly adh r h en successfully s l d, idizinggases such as N02 and 02 from the anode,

One of the difficulties which has been expers no chemical efiect npreserving he p o ienced in the electrolytic quantitative determinatlyte w thi d s red limits or in pr tion of copper and lead has been thefact that Venting imbalance d resulting O f q Q the oxygen whichaccumulates upon the anode the electrolyte wi h n equent formation ofduring the electrolysis tends to adhere firmly to p ngy andirregular-shaped and loosely adherthe anode and to oxidize any nitricacid present i s deposits of cop and P1 2 p he oath: in the electrolyteto ammonia and N02 and these Ode and de c i yreover. the use gasesmigrate to and tend to accumulate upon O rotating "5 fi i onl tends odislodge the cathode and anode, respective1y,-where they the depositaccumulated thereon but renders it retard deposition, cause spongydeposits of copdifiicult to maintain the characteristics of the per andPbOz, and otherwise generally cause incurrent and of the electrolyteemployed constant accurate quantitative results, unless eliminated.during the electrolysis.

Another difficulty which has been experienced Accordingly, an object ofthe present invention in the use of prior methods and apparatus for isto provide a new and improved apparatus for i the quantitativeelectrolytic determination of the quantitative electrolyticdetermination of copper and lead is the fact that oxidizing gases,copper andlead in copper-bearing andlead-bearsuch as N02 and 02, formedin the electrolyte I ing metals and ores and which, in use, overcomeduring the electrolysis, tend. to migrate to andto he f oi g and Otherdifliculties Xp amazes 3 in the use of prior methods and apparatus forthe quantitative electrolytic determination of copper and lead.

An additional object of the present invention is to provide a new andimproved apparatus for the quantitative electrolytic determination ofcopper and lead and in the use of which more exact and more rapidquantitative electrolytic determinations of these metals can be madethan has been possible heretofore in the use of prior method andapparatus.

A further object of the invention is to provide a new and improvedapparatus for the quantitative electrolytic determination of copper andlead and in the use of which deposition-retarding and oxidizing gases,such as N02 and 02, which tend to gather upon and to adhere to theanode, and to cause spongy and loosely held deposits thereon, arecontinuously and thoroughly removed from the anode during theelectrolysis without dislodging therefrom the PbO2 deposited thereon.

Still another object of the invention is to provide a new and improvedapparatus for the quantitative electrolytic determination of copper andin the use of which the internal resistance of the electrolyte isminimized.

Another object of the present invention is to provide a new and improvedapparatus for efiecting the relatively rapid and yet highly accuratequantitative determinations.

In the drawing:

Fig. 1 is a side elevational View, partly in section. illustrating apreferred form of electrolysis apparatus embodying the presentinvention;

Fig. 2 is a vertical sectional view illustrating the construction of theanode and related parts of the electrolysis apparatus shown in Fig. 1;

Fig. 3 is a bottom plan view, looking in the direction of the arrows 33in Fig. 2, illustrating the construction of the new anode apparatusshown in Fig. 2;

Fig. 4 is a top plan View, looking in the direction of the arrows l-4 inFig. 2, of the new anode apparatus shown in Fig. 2; and

Fig. 5 is a partial sectional plan view on line 5-5 in Fig. 1.

A preferred form of the new electrolytic apparatus is illustrated in thedrawing, wherein it is generally indicated at I0, and comprises an anodeunit, which is generally indicated at II, and a cathode unit which isgenerally indicated at 2, both of which are shown as being arranged inan electrolytic beaker I3. The anode unit I I includes a tubular metalcombination current-conducting and gas-conducting member I4 to which alead-in conductor I5 may be attached for connection to a suitablecurrent source. The anode unit I I also includes a preferablysandblasted and substantially cylindrical platinum wire gauze electrodeit of suitable mesh. The combination current-conducting andgas-conducting tubular member It extends through a central opening I8which is provided in a spider member I1 which is attached in anysuitable manner, as by a friction fit, upon the open upper end portionof the platinum wire gauze anode electrode I6 (Figs. 2 and 4). The lowerend portion I9 of the combination currentconducting and gas-conductingtubular member I4 extends downwardly below the open lower end of theplatinum wire gauze anode electrode l6 where the said lower end portionI9 of the said tubular member I4 is secured, in any suitable manner, asby welding, in a central opening 29 which is formed in a substantiallycircular closure member or cap 2| having an upper flanged portion 22which is attached in any suitable manner, as by welding, to the outersurface of the lower end portion of the substantially cylindricalplatinum wire gauze anode electrode I6 (Figs. 2 and 3). As shown inFigs. 2 and 3, the lower end portion I9 of the tubular member I4 has anopen lower end 24 which opens onto and below the lower surface 25 of theclosure member or cap 2| and which is curved convexly downwardly, asbest shown in Fig. 2.

The anode unit II is completed by a flexible rubber tubular member 28which is attached to the open upper end portion of the combinationcurrent-conducting and gas-conducting tubular member I4 so that the saidtubular member I4-28 may be connected to a suitable source of carbondioxide under pressure of from 1 to 15 pounds per square inch.

A procedure-that'is preferably followed in connection with the practiceof the present invention for dissolving the copper-containing andlead-containing metal to be analyzed is disclosed in my aforesaidpatent, the disclosure of which patent is herein incorporated byreference with respect to the preferred analytical methods to befollowed when using the apparatus of the present invention.

After the solution containing the metals to be analyzed is prepared asaforesaid, the solution thus prepared is then transferred to the beakerI3 (Fig. 1) and the anode unit I I and the cathode unit I2 are immersedtherein whereupon the control valve (not shown) for the CO2 supply tothe combination current-conducting and gas-conducting member I428 isadjusted to produce a steady flow of CO2 at a selected pressure of from1 to 5 pounds per square inch through the tubular member I428, whereuponthe current from the lead-in conductors I5 and 2'! to the anode andcathode units II and I2, respectively, is turned on. The electrolysisthereupon proceeds in the electrolysis beaker I3, the copper content ofthe electrolyte being deposited as metallic copper upon thesubstantially cylindrical platinum gauze cathode 29 and. the leadcontent of the electrolyte being deposited as PbOz upon thesubstantially cylindrical platinum gauze anode IS.

The current to the lead-in conductors I5 and. 21 and the flow of CO2through the tubular meinber I4.26 may then be shut off and the anode andcathode units I I and I2 respectively, removed from the beaker I3, andthe weight of the metallic deposits thereon is determined and theamounts of copper and lead in the sample res-pee tively calculated.

It has been found in the practice of the present invention that as theCO2 flows downwardly through the combination tubular current-com ductingand gas-conducting anode member I it emerges in the form of a steadystream of CO2 bubbles from the open lower end 2 2 of the tubular memberI 4 whence the CO2 bubbles pass upwardly over the convexly downwardlycurved bottom surface 25 of the closure member or cap 2i which isattached to the lower end portion of the substantially cylindricalplatinum gauze anode member I6.

Moreover, it has also been found in the practice of the presentinvention that as the CO2 bubbles emerge from the open lower end portion24 of the tubular member I4 and travel upwardly in the electrolyte overthe convexly downwardly curved lower surface 25 of the member 2! thesaid convexly downwardly curved lower surface 25 of the member 2!imparts a whirling motion to the C0 bubbles and as the stream ofwhirling CO2 bubbles pass upwardly in the electrolyte over the externalsurface of the substantially cylindrical platinum auze anode it and thesaid CO2 bubbles create a turbulence and exert a scouring action uponthe said platinum gauze anode l6, and upon the deposit of PbOz thereonand which results are not obtained when the bottom of the closure member211 is formed as a square or other substantially flat surface. In thismanner substantially all of the deposition-retarding and oxidizinggases, including O2 and N02, which accumulate upon the platinum gauzeanode l6 and upon the PbOz deposit thereon (and whichdeposition-retarding and oxidizing gases would otherwise cause spongyand loosely held deposits of PbO2 as well as building up the internalresistance of the electrolytic cell), are removed from the platinumgauze anode it and the PbOz deposit thereon in status nascendi. In thismanner good uniform and firmly held deposits of P1002 on the anode 16are assured, the internal resistance of the electrolytic cell isminimized and overvoltage in the electrolytic cell is eliminated,oxidation and resulting staining of the copper deposited on the cathode29 are prevented and good firm deposits of salmon-colored copper on thecathode 29 are obtained, the tendency of the ferric nitrate content inthe elecrolyte to increase with resultant corresponding increase in thesolvent action of the ferric nitrate upon the copper deposited on thecathode 29 is counteracted and reduced, and more accurate quantitativeelectrolytic determination of both lead and copper are assured.

It has also been found in the practice of the present invention that thesteadily flowing stream of CO2 bubbles thus passed into the electrolytenot only exerts a mechanical scouring or cleaning function upon theplatinum anode l6 and upon the PbOz deposit thereon, so as to remove instatus nasoendi the deposition-retarding and oxidizing gases, such as 02and N02, which would otherwise adhere and cling to the cathode l6 andthe PbO2 deposit thereon, but the steady flow of CO2 thus passed intothe electrolyte during the electrolysis performs a second but not fullyunderstood function which is believed to reside in the formation ofcarbonic acid (H2003) in the electrolyte and which tends to neutralizethe NHz which is formed in the electrolyte, particularly in the latterstages of the electrolysis. Hence it is believed that the 002 thusfunctions to maintain a definite acidity in the electrolyte throughoutthe electrolysis and thus keeps the temperature of the electrolyte down,preserves a more uniform current flow through the electrolyte, and thusaccelerates and promotes the deposition of the last traces of copper andlead in the clos trolytc upon the cathode and anode, respectively, withcorrespondingly more accurate quantitative electrolytic determinationsof these metals than has been possible heretofore in the use of priorapparatus. That such a second function is performed by the CO2, inaddition to its function of mechanically scouring the platinum anode l8and the PbOz deposit thereon, is shown by the fact that if a stream ofair is passed through the tubular anode member l l-28, in place of astream of CO2, but under otherwise identical conditions, and with allother variables controlled, the resuits in terms of quantitativeelectrolytic determinations of copper and lead are significantly andconsistently less accurate than when a stream of CO2 is directed alongthe sides of the anode, as in the practice of the present invention.That this is so may be seen by referenc to the comparative examplesdisclosed and contrasted one with the other in my aforesaid patent,which comparative examples relate to brasses described therein as beingof known compositions.

It will thus be seen from the foregoing descrip tion, considered inconjunction with the accompanying drawing, that the present inventionprovides a new and improved apparatus for the rapid and accuratequantitative electrolytic determination of lead and copper inlead-bearing and copper-bearing metals, ores, and the like, and that theinvention thus has the desirable advantages and characteristics, andaccomplishes its intended objects, including those hereinbefore pointedout and others which are inherent in the invention. While the apparatushas been described hereinabove from the standpoint of an analysis of acopper-lead sample along the lines disclosed in my aforesaid Patent No.2,544,802, it will be appreciated that the present apparatus may also beutilized in other types of electrolytic analyses wherein it may bedetermined that a scavenging action may be had at the anode by means ofthe apparatus of the present invention.

I claim;

1. In an electrolytic apparatus for quantitative determination ofsolutions, an electrode unit comprising, a substantially cylindricalplatinum gauze electrode adapted to be immersed in the solution, thebottom of the said gauze electrode being closed by a convexly roundedand imperforate closure member provided at its bottom center with apassage extending therethrough to open into the interior of saidcylindrical electrode, and a hollow tubular current-conducting elementextending longitudinally of and substantially centrally in the saidgauze electrode, one end portion of the tubular element being adapted tobe connected to a source of CO2 gas, the other end portion of thetubular element being sealably positioned in the said passage wherebyC02 gas conducted through said tubular element will bubble upwardlyalong the outer sides of the closure member to clean adherent oxidizinggases from the outer sides of the gauze electrode during electrolysis.

2. An electrode unit adapted to be immersed in a solution of anelectrolyte and adapted to cooperate electrically with another electrodefor quantitatively determining the cation content of said electrolyteand comprising, a substantially cylindrical platinum gauze electrode, animperforate closure member sealed to the bottom of said gauze electrodeand being provided with a passage centrally located in the bottomthereof, the side walls of said closure member being convexly taperedupwardly from said passage toward the bottom edge of said gauzeelectrode, and a hollow tubular gas-conducting element extendinglongitudinally of and axially through the gauze electrode, the upperopen end portion of the said tubular element being adapted to beconnected to a source of CO2 gas, the lower end portion of the saidtubular element being sealably positioned in the said passage in thesaid closure member whereby CO2 gas conducted downwardly through saidtubular element will bubble upwardly along the outer sides of theclosure member to scavenge the outer sides of the gauze electrode duringelectrolysis.

3. An electrode unit adapted to be used in conjunction with anelectrolytic apparatus for the quantitative determination of solutionscomprising, a substantially cylindrical and hollow electrode having atthe lower end thereof a generally rounded and upwardly curved cup-shapedbottom portion which is imperforate except at the central point whereata passage is formed therethrough to open into the interior of saidelectrode, the rim of said bottom portion coinciding substantially withthe bottom edge of said cylindrical electrode, and an elongatedgas-conducting tube connected to said passage at the inside of saidcylindrical electrode, said tube being extended axially of and throughsaid cylindrical electrode to be connected with a source of gas underpressure whereby said gas may be conducted to said passage in saidbottom portion to exit therefrom and bubble upwardly along the sides ofsaid bottom portion and said substantially coinciding rim and bottomedge to purge adherent gases and other foreign matter tending toaccumulate on the outer sides of said cylindrical electrode during usthereof.

ROBERT W. NOTVEST.

References Cited in the file of this patent Transactions of TheElectrochemical Society, V0176 (1939), pages 63-68,

Zeitschrift fur Elektrochemie, vol. 17 (1911), pages 905, 906.

1. IN AN ELECTROLYTIC APPARATUS FOR QUANTITATIVE DETERMINATION OFSOLUTIONS, AND ELECTRODE UNIT COMPRISING, A SUBSTANTIALLY CYLINDRICALPLATINUM GAUZE ELECTRODE ADAPTED TO BE IMMERSED IN THE SOLUTION, THEBOTTOM OF THE SAID GAUZE ELECTRODE BEING CLOSED BY A CONVEXLY ROUNDEDAND IMPERFORATE CLOSURE MEMBER PROVIDED AT ITS BOTTOM CENTER WITH APASSAGE EXTENDING THERETHROUGH TO OPEN INTO THE INTERIOR OF SAIDCYLINDRICAL ELECTRODE, AND A HOLLOW TUBULAR CURRENT-CONDUCTING ELEMENTEXTENDING LONGITUDINALLY OF AND SUBSTANTIALLY CENTRALLY IN THE SAIDGAUZE ELECTRODE, ONE END PORTION OF THE TUBULAR ELEMENT BEING ADAPTED TOTBE CONNECTED TO A SOURCE OF CO2 GAS, THE OTHERE END PORTION OF THETUBULAR ELEMENT BEING SEALABLY POSITIONED IN THE SAID PASSAGE WHEREBYCO2 GAS CONDUCTED THROUGH SAID TUBULAR ELEMENT WILL BUBBLE UPWARDLYALONG THE OUTER SIDES OF THE CLOSURE MEMBER TO CLEAN ADHERENT OXIDIZINGGASES FROM THE OUTER SIDES OF THE GAUZE ELECTRODE DURING ELECTROLYSIS.